out of recollection i think that you need to break the barrels to then access the actual tournaments where you vs cloud/vincent and after that you can access it. Im not sure i cant quite remember, but i know that you wont finish the game i dont think without completing that stage.

Its been a while since iv played KH, i think ill restart it, im just really eager since i saw some screens of KH2 a few days ago.

but yeah if im wrong then just go to a guide on the net or if your against that then maybe someone else can help, but my advice is just keep trying with the barrels, its hard when you first try them but you will get the hang of it.

btw cant you hit barrels or throw barrels at other ones to break 2 or 3 in one go?